b 8 + b 4 + 1 =
= b 8 + b 4 + 1 + b 4 − b 4 =
= b 8 + 2 b 4 + 1 − b 4 =
= ( b 4 ) 2 + 2 ( b 4 ) + 1 − b 4 =
= ( b 4 + 1 ) 2 − ( b 2 ) 2 =
= ( b 4 + 1 + b 2 ) · ( b 4 + 1 − b 2 )